1. Field of the Invention
The present invention relates to a fastener stringer for a slide fastener which is used in stretchable clothes such as sporting clothes, and in particular, relates to a fastener stringer for a slide fastener which is capable of preventing occurrence of chain breaking even when an element attaching portion is stretched.
2. Description of the Related Art
In the related art, a slide fastener has been used in various products such as clothes, bags and the like. For example, slide fasteners have also been used popularly in stretchable clothes such as knit fabric clothes and sporting clothes. Slide fasteners used in various kinds of stretchable clothes need to be attached to the clothes with excellent appearance and to be adapted to expansion and contraction of the clothes. Therefore, some stretchability is added to a fastener tape by selecting weaving structure or knitting structure, material of composition yarns or the like when the slide fastener tape is woven or knitted. Further, it has been known that the appearance of the slide fastener formed with a woven fastener tape is generally better than that formed with a knitted fastener tape.
In the case that some stretchability in the tape longitudinal direction is added to the fastener tape of the slide fastener, the element attaching portion to which the fastener element formed at one side edge of the fastener tape is configured not be stretchable while adding appropriate stretchability to the tape main portion of the fastener tape in the tape longitudinal direction by utilizing elastic yarns for some warp yarns, for example.
The reason is as described in the following. For example, in the case that some stretchability is added to both of the tape main portion and the element attaching portion of the fastener tape, when the element attaching portion of the fastener tape is stretched, an element row which is attached to the element attaching portion is stretched accordingly. When the fastener tape is stretched in a state that the bilateral fastener element rows are coupled and the element rows are stretched to some extent or more in the tape longitudinal direction, the coupling of the elements is released. Thus, a problem of the slide fastener opening laterally which is called chain breaking is apt to occur. For this reason, with a general slide fastener, the element attaching portion of the fastener tape is often configured to be non-stretchable.
For example, assuming that the slide fastener of which tape main portion is configured to be stretchable and of which element attaching portion is configured to be non-stretchable is attached to stretchable clothes, in this case, when a user performs an exercise such as stretching his or her body while wearing the stretchable clothes, the element attaching portion is not stretched while the tape main portion is stretched or contracted in accordance with the stretching or contraction of the clothes. Therefore, a strained phenomenon may occur at the clothes to which the slide fastener is attached. In addition, terrible disharmonized feeling may be induced in appearance when such clothes are worn.
In order to solve such a problem, a slide fastener which has some stretchability added to a vicinity of the element attaching portion as well as to the tape main portion has been disclosed, for example, in Japanese Patent Application Laid-Open No. 63-294804 and Japanese Patent Application Laid-Open No. 2008-43432.
For example, the slide fastener disclosed in JP-A No. 63-294804 includes elastic yarns (Spandex covered yarns) which are arranged regularly at specific intervals and non-stretchable yarns which are arranged at the rest of the part as warp yarns constituting the tape main portion and the element attaching portion of the fastener tape when the fastener tape is woven. Further, a coil-shaped element row in which a core thread is inserted is sewn to the element attaching portion of the fastener tape with a sewing yarn. The core thread is configured so that an elastic yarn is covered with a cover layer which is formed of a polyester bulky processed yarn (non-elastic yarn).
The slide fastener of JP-A No. 63-294804 having the abovementioned configuration has a degree of stretching that the element attaching portion is stretched by 10% or more when a load of 4 kg is applied to the fastener tape in the longitudinal direction, for example, since the elastic yarns are arranged regularly at specific intervals also at the element attaching portion similarly at the tape main portion.
On the other hand, a ratio of the quantity of arranged elastic yarns at the element attaching portion is the same as that at the tape main portion so that numerous non-stretchable yarns are woven also at the element attaching portion. Then, a degree of stretching of the core thread itself is suppressed by being covered with the cover layer which is formed of non-stretchable yarn. Further, the element row and the core thread are sewn to the element attaching portion with a non-stretchable yarn. With this configuration, a pitch between adjacent elements in a state that the fastener stringer is stretched most is limited to less than twice the length of the coupling head of the element row in the tape longitudinal direction.
Accordingly, in the case that the slide fastener of JP-A No. 63-294804 is attached to clothes having stretchability, a slide fastener attaching portion is stretched or contracted in accordance with the stretching of contraction of the clothes. Therefore, the strained phenomenon and disharmonized feeling are not induced so that comfortable wearing feeling and excellent appearance can be obtained. Here, the maximum stretching amount of the element row is limited as described above while some stretchability is added to the element attaching portion of the fastener tape. Therefore, even when the element attaching portion is stretched, occurrence of the chain breaking in the slide fastener due to release of coupling of the fastener elements can be prevented.
Moreover, a slide fastener of which stretchability is further enhanced than the slide fastener of JP-A No. 63-294804 is described in JP-A No. 2008-43432. For example, for sporting clothes, further enhanced stretchability is desired and developed in order to improve the product value. Accordingly, further enhanced stretchability has been desired for a slide fastener which is attached to such clothes having enhanced stretchability.
Then, in the slide fastener (fastener stringer) described in JP-A No. 2008-43432, an elastic yarn and a non-elastic yarn are woven in combination serving as the warp yarns at the tape main portion and the element attaching portion of the fastener tape. Further, the weaving ratio of the elastic yarn to the non-elastic yarn at the element attaching portion is set to be larger than that at the tape main portion.
In this manner, by varying the weaving ratio of the elastic yarn at the element attaching portion from that at the tape main portion so that the weaving ratio is larger than that at the tape main portion, the stretchability of the element attaching portion can be greatly enhanced. Specifically, the slide fastener of JP-A No. 2008-43432 is described to possess a degree of stretching with the element attaching portion being stretched by 10% or more when a load of 1 kg is applied to the fastener tape in the longitudinal direction.
Thus, the element attaching portion of the slide fastener of JP-A No. 2008-43432 is capable of being stretched with a small load and has excellent degree of stretching (stretchability) compared to that of the slide fastener of JP-A No. 63-294804. Therefore, even in the case that the slide fastener of JP-A No. 2008-43432 is sewn to fabric having high stretchability, for example, the fastener tape can be easily stretched and contracted smoothly following operation of stretching and contraction of the fabric. Therefore, the strained phenomenon and disharmonized feeling are not induced so that comfortable wearing feeling and excellent appearance can be obtained.
Further, in the fastener stringer of JP-A No. 2008-43432, the stretching amounts of the element attaching portion, the element row and the core thread in the longitudinal direction are limited so that the pitch between the fastener elements in the most stretched state is less than twice the length of the coupling head of the element row in the longitudinal direction. Accordingly, JP-A No. 2008-43432 describes that the chain breaking due to release of coupling of the fastener elements is to be prevented even when the element attaching portion is stretched in the state that the bilateral element rows are coupled.
The slide fasteners having base structure of which fastener tape is stretchable in the tape longitudinal direction are disclosed in JP-A No. 63-294804 and JP-A No. 2008-43432. Although the configuration of each of the fastener elements which forms the element row of the slide fastener is not described in detail, it is supposed from the disclosure that the element row is formed by utilizing a coil-shaped continuous fastener element which is generally used in the related art.
In this case, the general coil-shaped fastener element of the related art is formed by utilizing synthetic resin monofilament of which section is circular. Forming process of the coil-shaped fastener element is described in detail in the following. First, the monofilament of which wire diameter (sectional diameter) is 0.6 mm, for example, is processed to be bent so that the monofilament is wound to be coil-shaped. Subsequently, a projecting portion which bilaterally bulges is formed locally at the monofilament by plastically deforming to be flat with stamping forming. In this manner, the coil-shaped continuous fastener element is formed.
In the abovementioned coil-shaped fastener element of the related art, in the case that the wire diameter of the monofilament is 0.6 mm, generally, the dimension of the coupling head in the tape longitudinal direction (mountain length H) is set to be 1.08 mm and the pitch P between the adjacent fastener elements in the tape longitudinal direction is set to be 1.40 mm considering the coupling strength of the element rows, slidability of a slider and the like. Further, also in the case that monofilament of different wire diameter is used, relative dimensions (ratios) of the mountain length H and the pitch P against the monofilament wire diameter is basically to be constant.
Here, when the coil-shaped fastener element is sewn to the abovementioned stretchable fastener tape, attaching of the coil-shaped fastener element is performed in a state that a predetermined tension force is applied by pulling the fastener tape in the tape longitudinal direction. Thus, the pitch P of the obtained slide fastener in the tape longitudinal direction of the fastener element is generally contracted to approximately 1.37 mm since the tension force of the fastener tape during element attaching is removed.
Here, a case that the element row is formed with a normal coil-shaped fastener element in the slide fastener of which fastener tape and the element row are stretchable in the tape longitudinal direction as mentioned above is described in the following. In the state that the bilateral element rows are coupled, the coupling head of each of the fastener elements enters between upper and lower leg portions of the element of the coupling counterpart so that the coupling heads of respective bilateral element rows are engaged.
Therefore, even when the slide fastener receives force to pull the fastener tape toward the outside in the tape width direction (lateral tension force) in the state that the element rows are coupled, for example, the pitch P of the fastener elements is not expanded and the bilateral coupling heads remain firmly engaged. Therefore, the coupling of the bilateral element rows is not disengaged and the coupled state of the element rows can be maintained.
However, when the stretchable slide fastener receives force to push the element rows in the tape front-back direction (pushing force) in the state that the element rows are coupled, for example, the element rows are locally curved or bent in the tape front-back direction due to the stretchability of the fastener tape. As a result, the pitch P of the fastener elements is expanded at positions where the element rows are curved or bent.
Before receiving the pushing force, the coupling head of the fastener element is engaged with the coupling head of the fastener element of the coupling counterpart which is attached at a predetermined pitch. However, when the pitch P of the fastener elements is expanded by receiving the pushing force, the coupling head at a part which receives the pushing force is disengaged from the fastener element of the coupling counterpart and the coupled state of the element rows cannot be maintained. Therefore, there is a problem that chain breaking is apt to occur at the element rows.